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1.
Two bottom-mounted recording Doppler current profilers (RDCP) were deployed at nearshore locations (approximately 3 and 8 km offshore, in about 18 m water depth) in the southeast Chukchi Sea, Alaska, from October 2009 to September 2010 (UTC) with the goal of linking observed wave activity—wind-sea and swells—to their synoptic drivers. The northerly RDCP recorded a total of 16 events of elevated wave states: 15 exceeding 1 m significant wave height (SWH), and 1 exceeding 2 m SWH. The southerly RDCP recorded a total of 25 events of elevated wave states: 23 exceeding 1 m SWH, 2 m exceeded on two occasions and a SWH of 3 m was observed. Detailed analysis of the three large events (i.e., SWH events ≥2 m), including comparison with high-resolution reanalysis wind data (North America regional reanalysis), strongly suggested the wave energy evolved from a distant storm and would be defined as swell. Due to the close proximity of the shoreline to the east of the instruments, wind speeds based on reanalysis were constrained so fetch was westerly. Wave direction was also westerly, varying about 25° to the north (clockwise) or the south (counterclockwise) from the wind direction which is believed to be influenced by fetch and the strong current flow located where the nearshore RDCPs were deployed. Shore-fast sea ice is also believed to play a role but shown to only dampen wave activity for 3 months (January–April 2010), thus implying early ice breakup in this nearshore region. Two events appeared to be driven by southwesterly winds associated with cyclonic systems that moved into the eastern Chukchi Sea and then stalled. However, the second storm event appeared to be driven by northwesterly winds associated with a cyclonic system over the Brooks Range, a less common occurrence. Given that the typical storm activity in the region occurs as storms move into the Bering Sea in fall, this represents another potential source for wave conditions posing danger to people on the water or to coastal infrastructure. 相似文献
2.
海南岛东南部海岸砂丘风暴冲越沉积记录 总被引：1，自引：0，他引：1
通过海南岛东南部海岸详细的古风暴学考察,在尖岭海岸发现了含有风暴冲越沉积物的海岸沙丘剖面,分别命名为JL-1和JL-2剖面,试图从海岸沙丘沉积记录中提取历史上的风暴事件信息。沉积物粒度、磁化率等参数的指标分析表明,这两个剖面含有典型的风暴冲越沉积物,利用放射性核素AMS14C测年、OSL测年分析,并结合历史文献记载,确定这些风暴沉积层是多次台风作用的产物,其形成机制与风暴浪越过海岸沙丘的堆积有关,风暴流越过沙丘顶部后不能回流,导致风暴流携带的沉积物迅速沉积。此外,依据Stockdon经验公式计算结果,该地点沉积记录所代表的最大风暴事件相当于100到200年一遇的重现期。研究表明,该处海岸沙丘冲越沉积含有南海台风强度与重现期的重要信息。 相似文献
3.
古风力是一项重要的古气候指标,其定量恢复是一个难题。风作用于水体产生的波浪大小间接地反映了风力,能够为古风力的恢复提供思路。发育于破浪带和冲浪回流带的破浪沙坝、沿岸沙坝分别记录了破浪和冲浪过程,作者分别介绍利用古湖泊中发育的破浪沙坝和沿岸沙坝进行古波况和古风力恢复的原理和操作流程。(1)根据破浪沙坝的几何形态,可以将其厚度与破浪水深建立函数关系,而破浪水深又由破浪波高决定,因此破浪沙坝厚度可以恢复破浪波高,据此可以进一步根据波浪统计关系恢复有效波高、根据风浪关系恢复风力。此方法依托以下3个参数: 单期次的破浪沙坝厚度、破浪沙坝的基座坡角、古风程。(2)沿岸沙坝厚度近似记录了冲浪的极限高度,后者受控于有效波高,据此也可以恢复有效波高和风力。此方法依托以下5个参数: 单期次的沿岸沙坝厚度、古(平均)水深、古风程、古风向相对于岸线的入射角、组成沿岸沙坝的沉积物粒度。上述2种方法综合性较强,涉及古风向、古地形坡度、风程或盆地直径、古水深等参数的恢复,需要综合运用古地貌恢复、去压实校正、古岸线识别、古水深恢复等技术,并需要结合波浪理论。古湖泊滨岸带地层中保存有大量的滩坝沉积,利用其恢复古波况和古风况具有一定的应用前景,能够有助于更详细地重建沉积盆地的古地理背景。 相似文献
4.
以2001年4月至2002年 6月内蒙中部地区逐时观测的土壤水分资料为基础，论证了该区日土壤水分和日平均风速的变化规律，统计分析了日平均风速与土壤水分对沙尘暴的成生综合贡献。得出的主要结论是：①该地区沙尘暴发生时日平均风速的最小值是 3．5 m／s。如果日平均风速大于 8．0 m／s，预示着有沙尘暴的发生。②在平均风速大于 3．5 m／s的条件下，观测样本中 18．4％日数发生沙尘暴，而81．6％日数没有发生。说明大风的天气条件不应当被视其为沙尘暴的唯一重要的因子。③在同一地点、同样的风力条件下，在沙尘暴发生时，日平均风速与日平均土壤水分呈明显的反相关变化；而它们的反相关关系不明显时，沙尘暴就很少发生。 相似文献
5.
内蒙古中西部地区土壤水分对沙尘暴的贡献 总被引：2，自引：0，他引：2
以2001年4月至2002年6月内蒙中部地区逐时观测的土壤水分资料为基础，论证了该区日土壤水分和日平均风速的变化规律，统计分析了日平均风速与土壤水分对沙尘暴的成生综合贡献。得出的主要结论是：①该地区沙尘暴发生时日平均风速的最小值是3．5m／s。如果日平均风速大于8．0m／s，预示着有沙尘暴的发生。②在平均风速大于3.5m／s的条件下，观测样本中18．4％日数发生沙尘暴，而81．6％日数没有发生。说明大风的天气条件不应当被视其为沙尘暴的唯一重要的因子。③在同一地点、同样的风力条件下，在沙尘暴发生时，日平均风速与日平均土壤水分呈明显的反相关变化；而它们的反相关关系不明显时，沙尘暴就很少发生。 相似文献
6.
Products of marine processes occupy a considerable vertical range, which varies along the shore. Extreme waves can both cause erosion and form depositional structures up to several metres above the high tide mark. Temporary supra-elevation of water level by surge or wave set-up shifts effects upward. The preservation potential of products of extreme storms is relatively high, when compared to those associated with more frequent events. The level to which coastal landforms develop depends upon the conditions under which they form; thus sand beach ridges which are related to fairweathcr periods have a restricted height range when compared to gravel beach ridges building up under extreme storms. The varied coastal scenery of eastern Ireland provides many examples of storm-related products (barriers. cliffs, platforms, etc.). They have been related to a latc-Holocene eustatic sea level or even a partly isostatically controlled raised late-Holoccne sea level, but both elevations and apparent tilts can be explained by longshore variations in waves, tides and surges. Such an explanation is more consistent with other studies of latc-Holocene coastal evolution around the Irish Sea basin. 相似文献
7.
The disastrous effects of numerous winter storms on the marine environment in the North Sea and the Baltic Sea during the
last decade show that wind waves generated by strong winds actually represent natural hazards and require high quality wave
forecast systems as warning tools to avoid losses due to the impact of rough seas. Hence, the operational wave forecast system
running at the German Weather Service including a regional wave model for the North Sea and the Baltic Sea is checked extensively
whether it provides reasonable wave forecasts, especially for periods of extraordinary high sea states during winter storms.
For two selected extreme storm events that induced serious damage in the area of interest, comprehensive comparisons between
wave measurements and wave model forecast data are accomplished. Spectral data as well as integrated parameters are considered,
and the final outcome of the corresponding comparisons and statistical analysis is encouraging. Over and above the capability
to provide good short-term forecast results, the regional wave model is able to predict extreme events as severe winter storms
connected with extraordinary high waves already about 2 days in advance. Therefore, it represents an appropriate warning tool
for offshore activities and coastal environment. 相似文献
8.
V. Sanil Kumar Glejin Johnson K. K. Dubhashi T. M. Balakrishnan Nair 《Natural Hazards》2013,69(1):509-522
We studied the wave characteristics during the very severe cyclonic storm THANE which crossed the east coast of India between Puducherry and Cuddalore based on waves measured at a location in Bay of Bengal at 14 m water depth. Objective of the paper is to document the highest wave height measured in the nearshore waters of east coast of India. On 29 December 2011, cyclone passed within 77–315 km of the wave measurement location with maximum wind speed of 46.3 m/s (90 knots) and resulted in maximum wave height of 8.1 m. Maximum wave height recorded is 0.54 times the water depth, and the ratio of crest height to wave height of the highest wave recorded is 0.65. Maximum value of significant wave height estimated using the parametric wave model for deep-water conditions is 6.4 m, whereas the measured value is 6 m indicating that parametric wave model estimates the wave height reasonably well (within 8 % error) during the cyclone period. 相似文献
9.
Donald R. Cahoon 《Estuaries and Coasts》2006,29(6):889-898
Storms have long been recognized as agents of geomorphic change to coastal wetlands. A review of recent data on soil elevation
dynamics before and after storms revealed that storms affected wetland elevations by storm surge, high winds, and freshwater
flushing of the estuary (inferred). The data also indicate that measures of sediment deposition and erosion can often misrepresent
the amount and even direction of elevation change because of storm influences on subsurface processes. Simultaneous influence
on both surface and subsurface processe by storms means that soil elevation cannot always be accurately estimated from surface
process data alone. Eight processes are identified as potentially influencing soil elevation: sediment deposition, sediment
erosion, sediment compaction, soil shrinkage, root decomposition (following tree mortality from high winds), root growth (following
flushing with freshwater, inferred), soil swelling, and lateral folding of the marsh root mat. Local wetland condition (e.g.,
marsh health, tide height, groundwater level) and the physical characteristics of the storm (e.g., angle of approach, proximity,
amount of rain, wind speed, and storm surge height) were apparently important factors determining the storm's effect on soil
elevation. Storm effect on elevation were both permanent (on an ecological time scale) and short-lived, but event short-term
changes have potentially important ecological consequences. Shallow soil subsidence or expansion caused by a storm must be
considered when calculating local rates of relative sea level rise and evaluating storm effects on wetland stability. 相似文献
10.
The storm impact scale of Sallenger (J Coast Res 890–895, 2000) was tested on a partially engineered beach. This scale is supposed to provide a convenient tool for coastal managers to categorize the storm impact at the shore. It is based on the relation between the elevation of storm wave runup and the elevation of a critical geomorphic or man-made structures in the present study. Two different approaches were tested to estimate the elevation of extreme storm wave runup: (1) a parametric model based on offshore wave conditions and local beach slope and (2) the XBeach process-based model that solves implicitly the runup. The study shows comparisons between impact regimes computed with the two methods and those derived from video observations acquired during 2 weeks while the site was battered by three consecutive storms. Storms scenario including wave conditions with higher return periods and different tidal range were also investigated. The advantages and disadvantages of the two methods used to compute extreme water level are then compared, and guidelines for the development of early warning system are drawn. 相似文献
11.
Gazi Md. Khalil 《Natural Hazards》1993,8(3):263-281
A very severe cyclonic storm with wind speeds of over 240 km/h struck the coastal areas of Bangladesh in the full moon night of 29 April 1991. The path of the eye, close to the shore, raised a storm surge of unusual height, reportedly more than 9 m above the mean sea level, which devastated the offshore islands and the mainland coast. The damage to the physical infrastructure of the port of Chittagong and adjoining industrial area has been colossal, and recovery will take years. Death tolls from the cyclone, storm surge and its aftermath exceeded 145 000 making it one of the world's major natural disasters of this century.This paper is concerned with examining the magnitude and intensity of the disaster. It analyses how the people of Bangladesh, and the environment in which they live, were affected by the cyclone. A brief account is presented of loss of life and of the damage suffered in various sectors, including agriculture, industry, and physical infrastructure.The paper lays emphasis on the need of building a sufficient number of multipurpose cyclone shelters in the disaster-prone coastal areas of Bangladesh. Adequate measures should be taken for evacuating people from vulnerable areas and putting them into these shelters in the event of a cyclonic storm. Simplification of the current cyclone warning system is recommended.The difficulties of providing relief to the survivors are discussed. And finally, the need for improvement of the communication infrastructure in the coastal areas is highlighted. 相似文献
12.
The cyclone wave parameters are predicted using Young’s parametric hurricane wave prediction model. The input cyclone tracks
for this work are obtained from Fleet Naval Meteorology and Oceanography Center, USA. Extreme value analysis is carried out
to obtain the wave heights and periods for 1 in 5, 10, 50 and 100 years return periods, respectively. The deep-water hindcast
wave corresponding to 100 years from probable directions are allowed to propagate to Visakhapatnam coastal waters using nearshore
spectral wind-wave mode. The offshore wave height for one in 100-year return period is 11.9 m, and the corresponding nearshore
wave height at 10-m water depth varies between 4.6 and 5.6 m depending on the directional spreading. Weibull distribution
is chosen to fit the 24 cyclonic data sets over a total period of 30 years (September 1972 to November 2002). This paper demonstrates
usefulness of Young’s wave model for deep-water extreme wave hindcasting. Further, the results of the present study would
be highly useful for assessing the design wave height for Visakhapatnam coast. 相似文献
13.
Florin I. Zăinescu Florin Tătui Nikolay N. Valchev Alfred Vespremeanu-Stroe 《Natural Hazards》2017,87(2):599-621
This paper presents an overview of storminess along the Danube delta coast since 1949 by analysing wind and wave data and discusses the influences of teleconnections on climate variability. To this end, a five-category storm classification is proposed based on wind speed intensity and storm duration. On average, this coast experiences 30 storms/year occurring predominantly in winter, three of them considered severe (categories III–IV). The extreme storms (cat. V) endanger most the coastal settlements and the back-beach ecosystems (sand dunes, wetlands, lagoons) and have a mean recurrence rate of 7 years, but occur with a large inter-annual variability more frequent during the late 1960s, the 1970s and the 1990s. The prevalence of northern storms, in particular for the severe ones (>90% frequency for wind speeds >20 m/s) is responsible for the vigorous southward longshore sediment transport, which shaped the Danube delta physiognomy over the last millennia. The application of the newly developed energetic (Storm Severity Index—SSI) and morphologic (Storm Impact Potential—SIP) proxies allowed the better assessment of both the storm strength and the temporal variation in storm energy. It appears that storm climate follows a cyclic pattern with successive periods of 7–9 years of high, moderate and low storminess in accordance with the main teleconnections patterns (North Atlantic Oscillation—NAO, East Atlantic oscillation—EA, East Atlantic/Western Russia—EAWR, Scandinavian oscillation—SCAND). If NAO succeeded to explain best most of the storminess evolution (r = ?0.76 for 1962–2005), it failed during the latest decade (since 2006) when an unprecedented low in storminess occurred. There is also evidence of increased southern circulation during the latter period, associated with a reversal of correlation with NAO (from negative to positive). Significant correlations were also found for the EA, EAWR and SCAND (r = ?0.55, 0.56, 0.55, respectively, significant at p < 0.01) for all the study period suggesting that besides NAO, the north-western Black Sea coast storminess is considerably influenced by several modes of climate variability, most notable the EA and the EAWR, which succeed to address the recent decrease in storminess. 相似文献
14.
沙尘暴灾害致灾因子三维联合分布与重现期探索 总被引：1，自引：0，他引：1
探讨多致灾因子对Copula联合分布模型在三维多致灾因子综合分析中的扩展.针对沙尘暴形成的3个基本条件:大风、丰富的沙尘源和不稳定的大气层结,以内蒙古镶黄旗1990-2008年的强沙尘暴灾害事件为案例,建立了经向环流指数、地面平均最大风速和地表土壤湿度3个基本特征变量的联合分布,计算了基于联合分布的联合重现期.研究表明,镶黄旗强沙尘暴事件的三维致灾因子符合Frank Copula函数构建条件,该函数能够很好地描述强沙尘暴灾害3个基本特征变量的联合分布,具备扩展到三维的能力.相对于二维Copula函数拟合效果,三维Frank Copula在中高尾部分的拟合有很大提高.三变量联合重现期的计算结果更加贴近实际情况. 相似文献
15.
The Kaskapau Formation spans Late Cenomanian to Middle Turonian time and was deposited on a low‐gradient, shallow, storm‐dominated muddy ramp. Dense well log control, coupled with exposure on both proximal and distal margins of the basin allows mapping of sedimentary facies over about 35 000 km2. The studied portion of the Kaskapau Formation is a mudstone‐dominated wedge that thins from 700 m in the proximal foredeep to 50 m near the forebulge about 300 km distant. Regional flooding surfaces permit mapping of 28 allomembers, each of which represent an average of ca 125 kyr. More than 200 km from shore, calcareous silty claystone predominates, whereas 100 to 200 km offshore, mudstone and siltstone predominate. From about 30 to 100 km offshore, centimetre‐bedded very fine sandstone and mudstone record along‐shelf (SSE)‐directed storm‐generated geostrophic flows. Five to thirty kilometres from shore, decimetre‐bedded hummocky cross‐stratified fine sandstone and mudstone record strongly oscillatory, wave‐dominated flows whereas some gutter casts indicate shore‐oblique, apparently mostly unidirectional geostrophic flows. Nearshore facies are dominated by swaley cross‐stratified or intensely bioturbated clean fine sandstone, interpreted as recording, respectively, areas strongly and weakly affected by discharge from distributary mouths. Shoreface sandstones grade locally into river‐mouth conglomerates and sandstones, including conglomerate channel‐fills up to 15 m thick. Locally, brackish lagoonal shelly mudstones are present on the extreme western margin of the basin. There is no evidence for clinoform stratification, which indicates that the Kaskapau sea floor had extremely low relief, lacked a shelf‐slope break, and was probably nowhere more than a few tens of metres deep. The absence of clinoforms probably indicates a long‐term balance between rates of accommodation and sediment supply. Mud is interpreted to have been transported >250 km offshore in a sea‐bed nepheloid layer, repeatedly re‐suspended by storms. Fine‐grained sediment accumulated up to a ‘mud accommodation envelope’, perhaps only 20 to 40 m deep. Continuous re‐working of the sea floor by storms ensured that excess sediment was redistributed away from areas that had filled to the ‘accommodation envelope’, being deposited in areas of higher accommodation further down the transport path. The facies distributions and stratal geometry of the Kaskapau shelf strongly suggest that sedimentary facies, especially grain‐size, were related to distance from shore, not to water depth. As a result, the ‘100 to >300 m’ depth interpreted from calcareous claystone facies for the more central parts of the Interior Seaway, might be a significant overestimate. 相似文献
16.
ABSTRACTThis study investigates the storm surge caused by Typhoon Hato, which severely affected Macau, Hong Kong, and other coastal cities in China on 23 August 2017. A typhoon and storm surge coupling model demonstrated that the maximum storm surge height reached nearly 2.5?m along the coast of Macau, while that in Hong Kong was slightly below 2?m. Furthermore, a field survey of urban flooding revealed evidence of a 2.25-m inundation in downtown Macau and a 0.55-m inundation on Lantau Island, Hong Kong, which were likely exacerbated by a combination of storm surge, heavy rainfall, and surface water runoff over a complex hilly terrain. Significant wave overtopping and runup also occurred in beach and port areas. A typhoon track analysis confirmed that several comparably strong typhoons have followed similar ESE to WNW trajectories and made landfall in the Pearl River Delta in the last few decades. Although Hato was not the strongest of these storms, its forward speed of about 32.5?km/h was remarkably faster than those of other comparable typhoons. Higher levels of storm signal warnings were issued earlier in Hong Kong than in Macau, raising questions about the appropriate timing of warnings in these two nearby areas. Our analysis of the storm’s pattern suggests that both regions’ decisions regarding signal issuance could be considered reasonable or at least cannot be simply blamed, given the rapid motion and intensification of Hato and the associated economic risks at stake. 相似文献
17.
K. V. S. R. Prasad S. V. V. Arun Kumar Ch. Venkata Ramu P. Sreenivas 《Natural Hazards》2009,49(2):347-360
The nearshore parameters, viz., wave runup, wave setup, and wave energy have been estimated during storm and normal conditions
of SW monsoon (June–September) and NE monsoon (November–February) by empirical parameterization along Visakhapatnam coast.
These results were compared with the field observations during three storms of SW monsoon season in the year 2007. The higher
nearshore wave energies were observed at R.K. Beach, Jodugullapalem beach, and Sagarnagar beach during both the seasons. During
storm events, the higher wave energies associated with higher wave runups cause severe erosion along the wave convergence
zones. The storm wave runups (SWRUs) were higher at R.K. Beach, Palm beach, Jodugullapalem beach, and Sagarnagar Beach. The
yearly low wave energy was observed at Lawson’s Bay with lowest wave runup, considered as safest zone. R.K. Beach, Palm beach,
and Jodugullapalem beach are identified as vulnerable zones of wave attack. It is noteworthy that in addition to wave energies,
wave runups and wave setups also play a vital role in endangering the coast. 相似文献
18.
苏干湖沉积物粒度组成记录尘暴事件的初步研究* 总被引：6，自引：13，他引：6
文章通过分析苏干湖表层沉积物、流域表层沉积物、大气降尘以及湖泊冰面囚固碎屑颗粒等的粒度组成,比较了流域地表沉积与湖泊沉积物粒度组成的差异和苏干湖表层沉积粒度组成的空间变化。初步认为苏干湖沉积物粗颗粒组分(>63μm)主要由风力搬运入湖,>63μm组分的含量可以用来指示研究区尘暴事件的演化。结合湖泊沉积岩芯纹层计数年龄,重建的1000年来尘暴演化历史显示,在1210A.D.之前尘暴事件较弱,且变化幅度较小;1210A.D.以来则表现出高频率或者高强度,其中13世纪上半叶以及17世纪的高值段与东部降尘变化历史一致。就气候变化的特征时段(中世纪暖期、小冰期等)而言,尘暴事件主要与气候变冷情况下较强的盛行风场有关;而极端干旱区有效湿度的增加可能有利于地表粉尘的释放,助长了尘暴事件的发生。 相似文献
19.
Chandan Chakraborty 《Geological Journal》1995,30(1):69-78
The orientations of elongate gutter casts occurring in inner shelf storm deposits of the Proterozoic Bijaygarh Shale Formation, India reveal a modal population oriented roughly parallel to the average trend of the associated wave ripples. Assuming that the wave ripple trend approximately represents the orientation of the contemporary shoreline, the shore-parallel gutters appear to have been formed by the geostrophic current. Some gutters oriented at high angles to the inferred shoreline presumably represent incision by wave orbital currents in a storm-induced combined flow regime. The gutters also show variations in the style of incision and infill, which may be useful in distinguishing between gutters formed by wave orbital and geostrophic currents, independently of their orientation pattern with respect to the palaeo-shoreline. 相似文献
20.
A Field Study of How Wind Waves and Currents May Contribute to the Deterioration of Saltmarsh Fringe
Deltaic landscapes, such as the Mississippi River Delta, are sites of extensive conversion of wetlands to open water, where increased fetch may contribute to erosion of marsh edges, increasing wetland loss. A field experiment conducted during a storm passage tested this process through the observations of wave orbital and current velocities in the fringe zone of a deteriorating saltmarsh in Terrebonne Bay, Louisiana. Incident waves seaward of the marsh edge and wave orbital and current velocities immediate landward of the marsh edge were measured. Through a dimensional analysis, it shows that the current and orbital velocities in the marsh fringe were controlled by the incident waves, inundation depth, submergence ratio, and vegetation density. Similarly, it is shown that the longshore currents in the inundated saltmarsh fringe depended on the local wave-induced momentum flux, vegetation submergence, and vegetation density in the fringe zone. The cross-shore current showed the presence of a return flow in the lower region of the velocity profile. A high correlation between the current direction and the local flow-wave energy ratio as well as the vegetation submergence and density is found, indicating the important role of surface waves in the fringe flow landward of an inundated wetland under storm conditions. The field observations shed light on the potential ecological consequences of increased wave activities in coastal saltmarsh wetlands owing to subsidence, sea level rise, limited sediment supply, increases in wind fetch, and storm intensity. 相似文献